Reciprocating cutter bar assemblies have been used to cut crops such as wheat, oats, rye, barley and soybeans for over a century. Reciprocating cutter bar assemblies are typically constructed of a number of knives fixed in a row to a knifeback that is driven in reciprocation.
Stationary guard fingers (also called guard points or guard tips) are mounted adjacent to the knives such that when the bar is driven in a reciprocating motion, the knives on the bar engage the stationary guard fingers to cut the crop therebetween.
Prior art knives generally comprise a rectangular base for mounting the knife to the reciprocating bar and have forward trapezoidal or triangular cutting sections with cutting edges that are obliquely arranged to the forward direction of travel. Knives with single cutting sections have been used as well as double knives with twin cutting sections arranged side by side. Usually, the length of all knives in the forward direction is identical, but also knives with staggered forward tips have been described. The cutting edges are smooth or serrated, i.e. provided with small notches for improving the cutting action, and thus comprise a number of troughs and peaks arranged in an alternating fashion.
In the prior art, the peaks of the serrated cutting edges of all knives are lying on parallel lines extending transversely to the forward direction, and the troughs of the cutting edges of all knives are also arranged on parallel lines extending transversely to the forward direction.
One problem with this arrangement is excessive wear on small localized areas of the guard fingers and of the cutting section of the knife, since wear mainly appears at the peaks of the serrations. This is particularly a problem at cutter bar assemblies with a double cut configuration, at which more than one cutting section passes over or through a single guard finger.
It is an object of the invention to provide a twin knife having a cutting section with serrated cutting edges that provides an extended lifetime of a guard finger that interacts with the knives and of the knives.